The present invention relates to a support assembly for the road wheels of a vehicle, and particularly to a support assembly for the driving wheels of a motor vehicle.
It is known that modern support assemblies for the driving wheels of motor vehicles have a very compact structure with integrated rolling bearings which are able simultaneously to perform multiple functions, such as that of wheel hub, bearing, shaft and spindle. The said bearings, usually of the mixed type having two inclined rings of balls, in fact comprise an inner, substantially cylindrical ring, provided at one end with a flange for fixing to a wheel of the motor vehicle and having an inner surface on which is formed a splined coupling, and an outer, substantially cylindrical ring, provided at an end opposite to the said end of the inner ring, with a flange for fixing to a suspension strut for the said wheel. Between the said rings the rolling elements are interposed, which roll in suitable tracks and are protected by known sealing assemblies, the inner ring is further keyed by means of the splined coupling to a shaft of a ball joint thus allowing the transmission of the driving couple to the wheel. A variant of the described bearing is also known, in which the inner ring is composed of two coaxial annular elements which are fitted together, a first of which carries the said splined coupling and a rolling track for a ring of rolling elements and has a sleeve end on which is mounted a second element carrying a second rolling track for a second ring of rolling elements.
The constructional arrangements described have certain disadvantages. In particular the arrangement with the inner ring formed as a single element is limited in the number of rolling elements which can be introduced, and therefore involves the necessity of making the bearings over size in order to avoid overloading them. The arrangement with an inner ring formed by two connected elements allows this disadvantage to be partly overcome in that it permits a higher number of rolling elements to be introduced thus achieving an optimum filling of the bearings. The transmission of the drive couple by means of a splined coupling, however, makes it necessary to adopt a high minimum thickness of the sleeve end on which the second element is mounted in order to avoid weakening of a strongly stressed zone. Since the maximum overall external dimensions of the bearing are fixed by the available space, which is the same for any type of bearing, this involves the necessity of using rolling elements (in this case balls) of a reduced diameter in order to remain within the overall dimensional limits. As is known, however, rolling elements of reduced dimensions have a reduced load bearing capacity and this largely nullifies the advantage deriving from filling the bearing well. Moreover, a perfect centring of the two component elements of the inner ring is necessary and this is expensive and requires difficult working of the coupling surfaces.